(IAAC) Obj: Xi Scorpius, Struve 1999 - Inst: 102 mm f/9.8 Achromatic refractor

Observer: Luis Arguelles
Your skills: Intermediate (some years)
Date/time of observation: July,15,1998 - 21:30 UT
Location of site: Santander - Spain (Lat , Elev )
Site classification: Suburban
Sky darkness: 4.5 <Limiting magnitude>
Seeing: 6 <1-10 Seeing Scale (10 best)>
Moon presence: None - moon not in sky
Instrument: 102 mm f/9.8 Achromatic refractor
Magnification: 25x, 50x, 100x, 200x
Object(s): Xi Scorpius, Struve 1999
Category: Multiple star.
Constellation: Sco
Data: mag 4.77  size 
Position: RA :  DEC :
Using the setting circles, I navigate from Antares towards this very
nice pair of double stars.  The first observation is made at 25x and
interestingly I observe them as something more than pinpoint
stars. Anyway, I don't seem confident at all to say that I observe an
elongation at 25x.
Nevertheless, at 50x, both Xi Scorpius and Struve 1999 are an easy
split with my 4" refractor. Xi Scorpius is located North from Struve
1999 and is a brighter pair, but the pair from Struve 1999 is easier
to split than Xi Sco. At this magnification I can not observe
difference in coloration in Struve 1999 and both components show more
or less the same magnitude.
On the other hand, I easily observe a nice difference in magnitude
from both components of Xi Sco. What is very interesting is to note
that these two double stars offer almost the same beauty as the
typical "doble-doble", Epsilon Lyra.
Using 100x, I observe a clear difference in magnitude in Struve 1999:
The western component is a bit brighter than the another one. Also, I
can't observe difference in coloration between them, and both
components are rendered as white with a very slight yellowish
tint. Maybe the low altitude of the star over the horizont makes it a
little yellow.
Again at 100x, the main component of Xi Sco appears white-light
yellow, while the secondary does have a very soft blueish coloration.
After removing the star diagonal, the main star of Xi Sco appears as
orangeish. The secondary is white or white-blue (??). I also confirm
the white coloration of both components of Struve 1999.
Optional related URLs: http://members.tripod.net/~whuyss
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